1. Field of the Invention
This invention relates to a semiconductor device manufacturing method comprising a step of making contact holes in a film to be processed, and more particularly to a semiconductor device manufacturing method which has improved a step of making small-diameter contact holes.
2. Description of the Related Art
With the recent miniaturization of LSI patterns, the diameter of contact holes is getting smaller and smaller and the pitch between contact holes is also becoming narrower. To form a pattern with such contact holes (or a contact pattern), an ultrahigh-resolution exposure device has to be used, which is a factor that increases the pattern forming cost.
To overcome this problem, the following method has recently been proposed: contact holes whose diameter is larger than the proper one are formed using an exposure device whose resolution is not high and then a pattern thickening material, etc. are formed on the sidewalls of the contact holes (e.g., refer to Jpn. Pat. Appln. KOKAI Publication No. 2006-276865).
With this method, however, since the distance between adjacent contact patterns becomes shorter, adjacent contact patterns short-circuit, which is a problem. To prevent short-circuits, there is a method of arranging contact patterns in a zigzag. In this case, the element area increases.
As described above, when an attempt is made to form very small contact patterns with a narrow pitch periodically, an ultrahigh-resolution exposure device (generally a high numerical aperture NA) is needed, which causes the problem of increasing the pattern forming cost. Moreover, in a method which needs no high-resolution exposure device by devising means of arranging contact patterns, the chip area increases, which is a problem.